Unusual white stain? But isn't calcium..

[alexsmith1]

Hi all,

I've just bashed washed my in-ground pool in preparation for my holiday's and noticed the following. If I brush/slash with water the marking disappears for a minute before returning. Anyone know what it is? I've never seen this before. Thanks!

PH: 7.7
TA: 100
FC: 7
CH: 375
CYA: 70
SALT: 5200
TEMP: 22c / 72f

 

[Rancho Cost-a-Lotta]

If you put a drop of muriatic acid on it and it fizzes, it's calcium.

A little bump for more help...

 

[YippeeSkippy]

Looks like efflorescence to me. One gets that when water behind plaster, grout, etc gets behind a wall. It then pushes the calcium /minerals forward.
A little diluted MA may help, but the only permanent cure is to keep the water from getting behind there.

Maddie

 

[alexsmith1]

Thanks for the comments guys & girls! What's weird and I should've mentioned it before is its around the whole pool! I'll try a little acid on there and see if it fizzes.

 

[Rancho Cost-a-Lotta]

Before I had my tiles blasted for calcium, I noticed the build up was worse at the vertical grout lines. You can see it in the "before" pic on the bottom.

 

[alexsmith1]

Hi @Rancho Cost-a-Lotta was your waterline ever up to those tiles? Thanks.

 

[Rancho Cost-a-Lotta]

Yes. The photos show the waterline after it was dropped for media blasting.